A via is simply a hole in the board with copper on the walls.
You should understand that the default via is at the minimum the typical board mfg can produce. It is not the recommended size. This goes for the default trace with as well. The minimum is very small and should only be used if absolutely required.
Via size 1.6 mm + (this is the OD of the via “pad”)
Via drill 0.8 mm +
Track width 0.5mm+ Higher on power and ground traces.
In the above + means or higher. If you have the room there is not need to make the traces small. This being your first board. With larger traces the board is more likely to survive a short. And if you make a mistake it is easier to solder a wire to a wide trace.